Polishing block



May 2, 1939. J GREEN 2,156,686

POLISHING BLOCK Fled 0G11. 20, 1937 2 Sheets-Sheet 2 BY/ ff.. fdr-A A TTORNEYS.

Patented May 2, 1939 PATENT OFFICE -ronlslnivo. BLOCK James Green,?Brackenridge Heights, Pa., asslgnorto Pittsburgh Plate Glass Company, Allegheny vania County, Pa., a corporation j of Pennsyl- .Appiicaaon october zo, 1937-, serial No. 169,982 6 diams. (ci. 51;-19'0 The present inventionrelates to vapparatus employed in the surfacing of plate glass and more particularly to an improved form of polishing block for use in such operation. v

The primary object of my invention is the pro'- vision of a new style of polishing block,the use of which effects a great increase in the life of felts combined therewith to carry the polishing rouge. a material increasein the rate of polishing and l0 a. general improvement in operatingeiilciency.l

'I'hisand other objects and advantages of my invention will become' more apparent during the course of the following detailed description.

' Briefly stated, my invention contemplates the use of a polishing block having the working surface thereof scored in suitable pattern as a carrier for the polishing felt.

The polishing of plate glass, after the rough irregularities have been ground away by the apt0 plication of coarse abrasives, is largely effected by rouge or other finely divided abrasive inthe form of a' water slurry. This rouge is pressed against the surface of the glass by a felt pad ing block with a number of grooves, pits, or

other suitable depressions, the life of the polishing felts is increased several fold and at the same time the number of blocks necessary to the polishing operation is reduced by approximately fifty per cent.

In the drawings forming a part of this application and wherein like numerals are employed to designate like parts throughout the same:

Figure 1 is a transverse sectional View ofa polishing block with a felt layer positioned thereon, taken substantially along the line I--I of Figure 2.

Figure 2 is a bottom plan view of one form of polishing block embodying my invention.

Figure 3 is a bottom plan view of a modified form of polishing block.

Figure 4 is a fragmentary sectional view on an enlarged scale taken substantially along the line IV-IV of Figure 3, showing a layer of felt in 5| position upon the block.

As shown in the drawings. a polishing block I of steeljor cast-iron is suspended upon the lower end of a vertical spindle 2 by means of a universal ball and socket joint 6 that not only permits rotation of the block I about the spindle 2, 5 but also-allows the block I to 'adjust itself to the plane of the surface of the glass being polished. Aclamping plate l6 secured to the block I by bolts 1 maintains properlrelationship between the mock and the spindle z. Usually a inlurauty of 1o blocks are mounted upon a rotatable spider which -is positioned'directly above the plate glass con- 'veylng apparatus.` The specific form of the spindles. spidersfand conveyors. however, is conventional and need not be described in detail. i5

lar shape extending substantially over the entire 20 v surface of the block I. A larger prominence II is 'left in the center of the working surface in order that the block I be not excessively weakened at the ball and socket joint 5. The working surface of the block I is bevelled at the edges I5 25 to permit a polishing felt I6 to be placed thereon without undue stress at the periphery. The polishing felt I6 as shown in Figures 1 and 4, covers or extends across the depressions or scorin'gs and is held in position upon the block I by 30 means of a clamping ring I'I abutting shoulders or lugs i8 projecting from the block I. If desired, the polishing felt -I6 may be cemented to the block I to eliminate the use of the annular ring i1 or similar clamping device. 35

Figures 3 and 4 illustrate a modification in which the Working surface of the polishing block is provided with a plurality of recesses 20 of circular form arranged in a/,regular pattern. The other features of the block are identical with the 40 block previously described.

The particular arrangement of the grooves or recesses is not of major importance to the success of my invention and instead of intersecting parallel grooves 8 and 9, a single spiral groove 45 smooth blocks. It has been found, however, that in operation this new style of polishing block increases the eifective life of the polishing felts carried thereon by approximately three hundred percent. This feature alone obviates the fre- 55 quent renewal of the polishing felts, thus reducing the maintenance costol the polishing 'operation.

In a series of tests, polishing felis carried by blocks formed in accordance with the provisions of the present invention ran for an average period of eighteen hundred hours before failurev while felts carried by conventional blocks having smooth working surfaces and operating under similar conditions ran for only six hundred hours. The reason for the phenomenal increase in the life of the felts is not at present clear. The results are the direct antithesis of what would normally be expected because it would naturally be assumed that the edges of the grooves or recesses in the polishing blocks would tend rapidly to wear away the felt layers along the lines of contact. Moreover, the reduction of the bearing surface of the blocks should apparently tend to increase the pressure upon the portions of the felt over the elevations of the surface of the blocks. Such increase in pressure would be expected to augment the wear upon the felts,

It is probable that as the felt` I6 is pressed into the recesses portions of the working face of the polishing block, a large percentage of the rouge, employed to aid in the polishing operation, is

'drawn up into the felt and this action results in the more rapid formation of a face essential to the most efficient polishing. This face, or layer of rouge, is evenly distributed over the felt, thus eliminating the possibility of the formation of hard spots with other accompanying disadvantages. The heavier layer of rouge formed on the face of the felt results in better contact with the glass plates and accordingly a more rapid polishing is effected.

It has been found that the number of polishing blocks carried byI the spiders may be reduced by half without impairment of the resulting polish. It will be seen, therefore, that by reducing the number of polishing blocks and by increasing the life of the polishing felts used thereon, the cost of felts for the polishing of plate glass is greatly lowered. l

It is to be understood that the .form of the apparatus herewith shown and described is susceptible of various changes and modifications without a departure from the spirit or scope of my invention as set forth in the appended claims.

,What I claim is:

l. In combination in apparatus for polishing glass plates, u metal polishing block, the 'working surface of which is scored to provide a plurality of depressions therein, a layer of resilient material adapted to receive a slurry of suitable abrasive covering the working surface of the block, and means'l or securing the layer of resilient material to the polishing block.

2. In combination in apparatus for polishing glass plates. a metal polishing block, the Working surface of which is provided with a plurality of recesses arranged in a regular pattern, a layer of resilient material adapted to receive a slurry of suitable abrasive covering the working surface of the block, and means for securing the layer oi resilient material to the polishing block.

3. In combination in apparatus for polishing glass plates, a metal polishing block having a grooved working surface, a layer of resilient material adapted to receive a slurry of suitable abrasive covering the working surface of the block, and means for securing the'layer of resilient material to the polishing block.

4.-In combination in apparatus for polishing glass plates, a -metal polishing block, the working surface of which is scored with intersecting grooves, a layer of vfelt covering the working surface of the block, and means for securing the layer of felt to the polishing block.

5. In combination in apparatus for polishing glass plates, a metal polishing block, the working surface of which is scored with a set of parallel groves, intersected by a second set of grooves, a layer of felt covering the working surface of the block, 'and means for securing the layer of felt to the polishing block.

6. In combination in apparatus for polishing plates, a polishing block of metal having portions of the working face thereof cut away to provide a scored surface and a covering of porous resilient material adapted to receive and hold a slurry of polishing rouge applied and secured directly to the Working surface of the block and extending over the scorings.

JAMES GREEN. 

